In my copending patent application I have disclosed a molten metal sampler formed partially of insulating material and partially of a good conductor of heat to control the cooling of the metal so that a high quality sample of metal will be obtained which can be readily analyzed in the metallurgical laboratory. The molten metal sampler of that invention can be made as a stream sampler or as an immersion sampler. In the former the sampler is especially adapted to be placed in the stream of metal as it flows from one container to another to receive the sample of molten metal. On the other hand, the immersion type sampler is especially adapted to be immersed in a melt of metal to obtain the sample. Thus, the sampler would be immersed in the metal as the latter is in a furnace, ladle or the like and the metal will flow into a sample chamber which is adapted to form and contain the desired sample.
In either case it may be desirable because of the conditions encountered to provide an aid for admitting the molten metal into the sample chamber and such aid is provided in the present invention by evacuating the sample chamber before placing it in use to create a vacuum therein and the chamber is sealed to maintain the vacuum. The seal is formed of a substance that will disintegrate when placed in the molten metal so that the metal will then flow freely into the evacuated chamber.
Such a vacuum assist to the flow of molten metal into the sample chamber is especially desirable when it is difficult or impossible to fully immerse the sampler into the molten metal as may occur when the melt is in a relatively shallow ladle or mold. Moreover, the evacuated chamber will produce a sample which is solid throughout and free of any voids so that a vacuum type sampler may be desirable to use under all conditions where an extremely high quality sample is required.
The advantages of vacuum type molten metal samplers has been previously recognized but they have been constructed in such a manner as to limit the shape of the sample that can be taken or they are inconvenient to operate in the vicinity of molten metal. Thus, vacuum type molten metal samplers are disclosed in U.S. Pat. No. 3,534,614 to Creswell and U.S. Pat. No. 3,369,406 to Lowdermilk et al. In both cases a tube made of glass or other impervious material is evacuated and sealed. The molten metal breaks the seal and flows into the tube. As a result, only a pin type sample can be taken with these constructions because the sample chamber itself is evacuated so that its configuration is strictly limited.
On the other hand, the present invention provides an arrangement in which the sample chamber is placed in an evacuated space so that the sample chamber itself can be of any desired shape. Accordingly the single sample chamber in the evacuated space can be shaped to form the well known paddle shape which produces surfaces that may be readily polished and at the same time can produce the pin for other metallurgical analyses.
The disadvantages of the limited configuration of vacuum type samplers was overcome by the sampler disclosed in U.S. Pat. No. 3,791,220 to Falk et al but it was accomplished by requiring the person taking the sample to operate a pump for reducing the pressure in the sample chamber while the sample is being taken. This requires the person to operate close to the molten metal which may be highly undesirable and virtually impossible under some conditions. This is avoided in the present invention by creating the vacuum before the sampler is placed in the molten metal so that the person taking the sample is not required to operate any mechanism but merely takes the sample in the conventional manner. Yet, the configuration of the sample is not strictly limited as it has been in other prior art vacuum type samplers in which the vacuum is created prior to inserting the sampler into the molten metal.